Levothyroxine sodium

Chemical Properties

Levothyroxine sodium is White Solid

Originator

Synthroid,Flint,US,1953

Uses

One of the thyroid hormones involved in the maintenance of metabolic homeostasis. Synthesized and stored as amino acid residues of thyroglobulin, the major protein component of the thyroid follicular colloid. Synthesis and secretion are regulated by the pituitary hormone (TSH). Deiodinated in peripheral tissues to the active metabolite, liothyronine. The D-form has very little activity as a thyroid hormone, but has been used to treat hyperlipidemia.

Indications

Levothyroxine sodium (Levothroid, Synthroid, Levoxine) is the sodium salt of the naturally occurring levorotatory isomer of T₄. It is the preparation of choice for maintenance of plasma T₄ and T₃ concentrations for thyroid hormone replacement therapy in hypothyroid patients. It is absorbed intact from the gastrointestinal tract, and its long half-life allows for convenient oncedaily administration. Since much of the T₄ is deiodinated to T₃, it is usually unnecessary to use more expensive preparations containing both T₄ and T₃.The aim is to establish euthyroidism with measured serum concentrations of T₄, T₃, and TSH within the normal range.
The TSH-suppressive effects of exogenous T₄ also prove useful in removing the stimulatory effects of TSH on the thyroid gland in the management of simple nonendemic goiter, chronic thyroiditis, and TSHdependent thyroid carcinoma.

Definition

ChEBI: The sodium salt of L-thyoxine. It is used as replacement therapy in the treatment of hypothyroidism.

Manufacturing Process

A 9.30 g portion of N-acetyl-L-diiodotyrosinamide was suspended in 100 ml of 0.05M boric acid (H3BO3) and 100 ml of 95% ethanol, and the solid was dissolved by adjusting the pH to 10.5 with 2N sodium hydroxide (NaOH). A 15% (by weight) portion of manganese sulfate monohydrate was added and the solution heated at 44°C under conditions of oxygenation while being agitated mechanically. After approximately 24 hours of incubation, the precipitated product was collected and separated from the catalyst, providing the amide of N-acetyl-L-thyroxine in 30.6% yield. On hydrolysis (removal of both amide functions), achieved by refluxing in glacial acetic acid-hydrochloric acid (approximately 2:1), L-thyroxine is obtained. It was isolated as the sodium salt, containing approximately 5 molecules of water of hydration.

brand name

Levo-T (Alara); Levolet (Vintage); Levothroid (Lloyd); Levoxyl (Jones); Novothyrox (Genpharm); Synthroid (Abbott); Unithroid (Stevens J).

Therapeutic Function

Thyroid hormone

General Description

Levothyroxine sodium,O-(4-hydroxy-3,5-diiodophenyl)-3,5-diiodo-2-tyrosinemonosodium salt, hydrate (Synthroid, Letter, Levoxine,Levoid), is the sodium salt of the levo isomer of thyroxine,which is an active physiological principle obtained from thethyroid gland of domesticated animals used for food by humans.It is also prepared synthetically. The salt is a light yellow,tasteless, odorless powder. It is hygroscopic but stablein dry air at room temperature. It is soluble in alkali hydroxides,1:275 in alcohol, and 1:500 in water, to give a pH ofabout 8.9.

Clinical Use

Liothyronine sodium occurs in vivo together withlevothyroxine sodium; it has the same qualitative activitiesas thyroxine but is more active. It is absorbed readily fromthe gastrointestinal tract, is cleared rapidly from the bloodstream,and is bound more loosely to plasma proteins than isthyroxine, probably because of the less acidic phenolic hydroxylgroup.Its uses are the same as those of levothyroxine sodium,including treatment of metabolic insufficiency, male infertility,and certain gynecological disorders.

Veterinary Drugs and Treatments

Levothyroxine sodium is indicated for the treatment of hypothyroidism in all species.